Microwave photoconductivity, photovoltaic properties and architecture of a polymer-semiconductor nanocrystal composite

We have studied composites of poly(p-phenylenevinylene) (PPV) and TiO2 nanocrystals with a time-resolved microwave conductivity technique, Rutherford backscattering, and photocurrent/photovoltage measurements. Photovoltaic devices of the structure (Al/PPV:TiO2 composite/ITO) exhibit a photocurrent which we suggest is due to both exciton generation in the polymer and free carrier generation above the bandgap in the TiO2 nanocrystals. The quantum yield of the latter part of the photocurrent is significantly higher (>10% above 3.4 eV) than for that part due to exciton generation in the polymer (1–2% between 2.4 and 2.7 eV).